Why are we attracted to people we know are trouble. People may assume they’re drawn to danger or risk taking. But in fact, people with dark personalities may look hotter when they try harder than do those with more stable character traits.

Scientists gave personality tests to more than 100 subjects to rate them for what’s called Dark Triad traits—that’s Machiavellianism, narcissism and psychopathy. They then took different photographs of each subject. One was a so-called “adorned condition” where the participants were turned out clothed and styled. In the “unadorned condition” they were presented as neutrally as possible: their hair was pulled back, they changed into grey sweat pants and tee shirts, and they wore no makeup or other adornments. And they maintained neutral facial expressions.

The pictures were then shown to volunteers who rated them for attractiveness. And the people who exhibited the Dark Triad traits were rated as significantly more attractive in the adorned state than in their unadorned state. But the subjects who did not have dark traits did not get an attractiveness boost from getting dressed up and coiffed. The study is the journal Social Psychological Personality and Science. [Nicholas S. Holtzman and Michael J. Strube, People with Dark Personalities Tend to Create a Physically Attractive Veneer]